Strength loss resistant methods for improving the softening of cotton toweling and related fabrics

ABSTRACT

Disclosed are strength loss resistant methods for treating cotton toweling with cellulase so as to impart permanent softening to the toweling. In particular, the methods disclosed herein involve the application of a specified amount of cellulase onto one or both of the surfaces of a cotton toweling so as to result in permanent softening of the toweling.

This application is a continuation of application Ser. No. 08/117,648filed Sep. 8, 1993, now U.S. Pat. No. 6,156,562 which in turn, is acontinuation of application Ser. No. 07/810,962 filed Dec. 20, 1991,which is now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to strength loss resistant methods fortreating cotton toweling and related fabrics with cellulase so as toimpart permanent softening to these fabrics. In particular, the methodsof the present invention involve the application of a specified amountof cellulase onto the surface fibers of cotton toweling and relatedfabrics so as to result in permanent softening of such fabrics. On theother hand, since a specified amount of cellulase is applied only ontothe surface fibers of such fabrics, the base fibers (i.e., the interiorfibers) of the fabric are not exposed to significant quantities ofcellulase. In turn, the interior fibers are not significantly degradedby cellulase and accordingly, strength loss in the treated fabric isreduced as compared to the strength loss arising from treating all ofthe fibers of the fabric with cellulase.

The methods of the present invention are particularly suitable for usein both a continuous and batch process for treating cotton toweling andrelated fabrics with cellulase.

2. State of the Art

The use of cellulase to impart permanent softening properties to cottontoweling and related materials is well known in the art. For example,cotton toweling can be treated in a batch or continuous process wherebythe treated fabric is washed (immersed) in a cellulase solution atspecified conditions. Under such conditions, both the interior and thesurface cotton fibers of the fabric are exposed to the cellulasesolution. After treatment, the fabric is generally rinsed and dried.Under these conditions, such treatment with cellulase results inpermanent softening for the fabric.

However, there is a problem with the treatment of cotton toweling andrelated fabrics in the manner of the prior art. Specifically, whentreated in heretofore known methods for imparting permanent softening,such fabrics experience undesirable weight loss, reduced tensilestrength and reduced absorbency. These detrimental attributes can be sosevere as to render the treated fabric a poorer quality product ascompared to the fabric prior to treatment.

In view of the above, methods for treating cotton toweling and relatedfabrics which impart permanent softening properties to such fabrics butwhich also result in reductions in the undesirable properties impartedby prior art processes would be particularly advantageous.

SUMMARY OF THE INVENTION

The present invention is directed to new methods for treating cottontoweling and related fabrics with cellulase so as to impart permanentsoftening to such fabrics. Unlike prior art processes for impartingpermanent softening to such fabrics by exposing the entire fabric to thecellulase solution, the present invention is directed to the discoverythat substantial and unexpected improvements are achieved when aspecified amount of cellulase is applied onto the surface(s) of cottontoweling and related fabrics (“cotton toweling” as defined hereinbelow). Specifically, the methods of the present invention impartpermanent softening to the so treated cotton toweling while alsoproviding for substantial reductions in strength loss, weight loss andloss of absorbency as compared to strength loss, weight loss and loss ofabsorbency achieved in cotton toweling treated with prior art processes.

Accordingly, in one of its method aspects, the present invention isdirected to a method for imparting permanent softening to cottontoweling by treatment with cellulase which method comprises:

(a) applying onto the surface or surfaces of said cotton toweling anaqueous cellulase solution comprising at least about 0.2 grams per litercellulase wherein the weight amount of said aqueous cellulase solutionapplied onto the surface(s) of said toweling is between about 10 to 50percent of the weight of said toweling; and

(b) maintaining said toweling under conditions sufficient to impartsoftening to said toweling.

In a preferred embodiment, the application of the aqueous cellulasesolution to the surface or surfaces of the toweling is by way ofspraying and even more preferably by a substantially uniform spraying ofthe aqueous cellulase solution over the surface or surfaces of thetoweling.

In another preferred embodiment, the application of the cellulasesolution is to both surfaces of the cotton toweling and even morepreferably, the application to both surfaces is conductedsimultaneously.

After treatment in the process of this invention, the cotton toweling isthen treated in a manner to remove and/or inactivate the cellulaseenzyme. One method of removing the enzyme is by thoroughly rinsing theso treated toweling with a cellulase free aqueous solution (i.e., anaqueous solution containing no cellulase). In such an embodiment, thetoweling is then dried at elevated temperatures to inactivate any enzymeremaining. Alternatively, the toweling is first treated to inactivatethe cellulase enzyme by heating to sufficiently high temperatures for asufficiently long period of time to inactivate the enzyme. In thisembodiment, after inactivation, the toweling can subsequently bethoroughly rinsed and dried.

In one of its articles of manufacture aspects, the present invention isdirected to cotton toweling which is permanently soft which toweling isprepared by the methods of this invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1A illustrates a plan view of a cotton toweling useful in themethods of this invention and

FIG. 1B illustrates an enlarged cross-sectional view of this fabrictaken along lines, 2—2.

FIG. 2 illustrates continuous and simultaneous application of an aqueouscellulase solution to both surfaces of cotton toweling.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As noted above, the present invention is directed to methods fortreating cotton toweling with cellulase so as to impart permanentsoftening to the toweling which methods involve applying an aqueouscellulase solution to the surface of the toweling. However, prior todiscussing this invention in further detail, the following terms willfirst be defined:

1. Definitions.

As used herein, the following terms have the meanings given below:

The term “toweling” refers to toweling as well as to related materialshaving a similar construction as toweling. In this regard, it is artrecognized that toweling is constructed by forming one or more loopswhich extend both above and/or below a plane of base fibers.Accordingly, related materials include, for example, velour, corduroy,and the like, which possess similar construction to toweling with theexception that some or all of the loops are clipped (broken).

The term “cotton toweling” refers to toweling made of 100% cotton orcotton blends. When cotton blends are employed, the amount of cotton insuch toweling should be at least about 40 percent by weight percentcotton; preferably, more than about 60 percent by weight cotton; andmost preferably, more than about 75 percent by weight cotton. Whenemployed as blends, the companion material employed in the fabric caninclude one or more non-cotton fibers including synthetic fibers such aspolyamide fibers (for example, nylon 6 and nylon 66), acrylic fibers(for example, polyacrylonitrile fibers), polyester fibers (for example,polyethylene terephthalate), polyvinyl alcohol fibers (for example,Vinylon), polyvinyl chloride fibers, polyvinylidene chloride fibers,polyurethane fibers, polyurea fibers and aramid fibers. It iscontemplated that regenerated cellulose, such as rayon, could be used asa substitute for cotton in cotton toweling.

The term “finishing” as employed herein means the application of asufficient amount of finish to the cotton toweling so as tosubstantially prevent cellulolytic activity of the cellulase on thetoweling. Finishes are generally applied at or near the end of themanufacturing process of the toweling for the purpose of enhancing theproperties of the toweling, for example, softness, drapability, etc.,which additionally protects the toweling from reaction with cellulases.Finishes useful for finishing cotton toweling are well known in the artand include, for example quatenary salts and other softners.

The term “cellulose” as employed herein refers to an enzyme compositionderived from a microorganism which acts on crystalline forms ofcellulose and its derivatives to hydrolyze cellulose and give primaryproducts, glucose and cellobiose. Such cellulases are synthesized by alarge number of microorganisms including fungi, actinomycetes, glidingbacteria (mycobacteria) and true bacteria. Some microorganisms capableof producing cellulases useful in the methods disclosed herein aredisclosed in British Patent No. 2 094 826A, the disclosure of which isincorporated herein by reference. Most cellulases generally have theiroptimum activity in the acidic or neutral pH range. On the other hand,alkaline cellulases, i.e., cellulases showing optimum activity inneutral or alkaline media, are also known in the art. Microorganismsproducing alkaline cellulases are disclosed in U.S. Pat. No. 4,822,516,the disclosure of which is incorporated herein by reference. Otherreferences disclosing alkaline cellulases are EPA Publication No.269,977 and EPA Publication No. 265,832, the disclosures of which arealso incorporated herein by reference.

Cellulase produced by a naturally occurring micro-organism is sometimesreferred to herein as a “cellulose system” to distinguish it from theclassifications and classification components isolated therefrom. Suchclassifications are well known in the art and includeexo-cellobiohydrolases (“CBH”), endoglucanases (“EG”) and β-glucosidases(“BG”). Additionally, there are multiple components in eachclassification. For example, in the cellulase obtained from Trichodermareesei, there are two CBH components, i.e., CBH I and CBH II, and atleast three EG components, EG I, EG II and EG III.

The different classifications are known in the art to synergisticallyinteract with each other to provide enhanced activity against cellulose.Thus, while a cellulase system derived from any microorganism can beemployed herein, it may be preferable that the cellulase system containat least one CBH component and at least one EG component so thatenhanced cellulase activity is achieved.

The fermentation procedures for culturing cellulolytic microorganismsfor production of cellulase are known per se in the art. For example,cellulase systems can be produced either by solid or submerged culture,including batch, fed-batch and continuous-flow processes. The collectionand purification of the cellulase systems from the fermentation brothcan also be effected by procedures known per se in the art.

Preferred cellulases for use in this invention are those obtained fromTrichoderma reesei, T. koningii, Pencillum sp., Humicola insolens, andthe like. Certain cellulases are commercially available, i.e.,CELLUCLAST (available from Novo Industry, Copenhagen, Denmark), RAPIDASE(available from Gist Brocades, N.V., Delft, Holland), CYTOLASE 123(available from Genencor International, South San Francisco, Calif.) andthe like. Other cellulases can be readily isolated by art recognizedfermentation and isolation procedures.

The term “surface active agent or surfactant” refers to anionic,non-ionic and ampholytic surfactants well known in the art.

The term “buffer” refers to art recognized acid/base reagents whichstabilize the cellulase solution against undesired pH shifts during thecellulase treatment of the cotton-containing fabric.

The term “aqueous cellulase solution” means an aqueous solutioncontaining cellulase and optional additives such as surfactants,buffers, and the like. In general, the aqueous cellulase solution willcontain at least about 0.2 grams of cellulase per liter and, preferably,from about 0.4 grams of cellulase to about 1.0 grams of cellulase perliter of solution. In this application, all references to grams ofcellulase per liter refer to grams of cellulase protein (CBH, EG and BGcomponents) with non-cellulase components being excluded.

Surprisingly, it has been found that it is the amount of cellulaseprotein and not its relative rate of hydrolysis of crystalline celluloseto glucose which provides for the improvements cited herein.

In order to improve the wettability of the solution, the aqueouscellulase solution may contain from about 0.1 to about 5 weight percentof a surfactant and preferably from about 0.2 to 2 weight percent ofsurfactant based on the total weight of the aqueous cellulase solution.

The aqueous cellulase solution is generally maintained at a pH where thecellulase possesses significant cellulolytic activity. In this regard,it is art recognized that cellulase activity is pH dependent. That is tosay that a specific cellulase composition will exhibit significantcellulolytic activity within a defined pH range with optimalcellulolytic activity generally being found within a small portion ofthis defined range. The specific pH range for cellulolytic activity willvary with each cellulase composition. As noted above, while mostcellulases will exhibit cellulolytic activity within an acidic toneutral pH profile, there are some cellulase compositions which exhibitcellulolytic activity in an alkaline pH profile.

During treatment of cotton toweling, it is possible that the pH of theinitial cellulase solution could be outside the range required forsignificant cellulase activity. It is further possible for the pH tochange during treatment of the cotton toweling, for example, by thegeneration of reaction product(s) which alters the pH of the solution.In either event, the pH of an unbuffered cellulase solution could beoutside the range required for significant cellulolytic activity. Whenthis occurs, undesired reduction or cessation of cellulolytic activityin the cellulase solution occurs. For example, if a cellulase having anacidic activity profile is employed in a neutral or alkaline unbufferedaqueous solution, then the pH of the solution will result in lowercellulolytic activity and possibly in the cessation of cellulolyticactivity. On the other hand, the use of a cellulase having a neutral oralkaline pH profile in a neutral unbuffered aqueous solution shouldinitially provide significant cellulolytic activity.

In view of the above, the pH of the cellulase solution should bemaintained within the range required for significant cellulolyticactivity. One means of accomplishing this is by simply adjusting the pHas required by the addition of either an acid or a base. However, in apreferred embodiment, the pH of the system is preferably maintainedwithin the desired pH range by the use of a buffer in the cellulasesolution. In general, a sufficient amount of buffer is employed so as tomaintain the pH of the solution within the range wherein the employedcellulase exhibits activity and preferably where the cellulase exhibitsoptimal activity. Insofar as different cellulase compositions havedifferent pH ranges for exhibiting cellulase activity, the specificbuffer employed is selected in relationship to the specific cellulasecomposition employed. The buffer(s) selected for use with the cellulasecomposition employed can be readily determined by the skilled artisantaking into account the pH range and optimum for the cellulasecomposition employed as well as the pH of the cellulase solution.Preferably, the buffer employed is one which is compatible with thecellulase composition and which will maintain the pH of the cellulasesolution within the pH range required for optimal activity. Suitablebuffers include sodium citrate, ammonium acetate, sodium acetate,disodium phosphate, and any other art recognized buffers. In general,such buffers are employed in concentrations of at least 0.005 N andgreater. Preferably, the concentration of the buffer in the cellulasesolution is from about 0.01 to about 0.5 N, and more preferably, fromabout 0.05 to about 0.15 N. In general, increased buffer concentrationsin the cellulase solution may cause enhanced rates of tensile strengthloss of the treated cotton toweling.

The tensile strength of cotton toweling can be measured in a warp andfilling direction which are at right angles to each other. Accordingly,the term “warp tensile strength” as used herein refers to the tensilestrength of the cotton toweling as measured along its length whereas theterm “filling tensile strength” refers to the tensile strength of thecotton toweling as measured across its width.

The tensile strength of cotton toweling is readily conducted followingASTM D1682 test methodology. Equipment suitable for testing the tensilestrength of such fabrics include a Scott tester or an Instron tester,both of which are commercially available. In testing the tensilestrength of cotton toweling which has been treated with a cellulasesolution in the manner of this invention, care should be taken toprevent fabric shrinkage after treatment and before testing. Suchshrinkage would result in erroneous tensile strength data.

2. Methodology

In the methods of the present invention, the aqueous cellulase solutionis applied onto the surface or surfaces of the cotton toweling in eithera continuous or batch process. Methods for applying the cellulasesolution to the surface of the cotton toweling include, by way ofexample, painting the solution onto the surface of the toweling,spraying the solution onto the surface of the cloth, and the like. Ineither case, while some of the cellulase solution may penetrate into theinterior fibers of the toweling, a substantial portion of the cellulasesolution will remain on the surface of the toweling.

In a preferred embodiment, the aqueous cellulase solution is applied toone or both surfaces of the toweling and preferably, the methods of thisinvention are conducted prior to the application of any finish to thetoweling.

Sufficient amounts of the aqueous cellulase solution are applied ontothe surface(s) of the toweling so that the weight amount of the solutionapplied onto the toweling is between about 10 to 50 percent of theweight of the toweling (before treatment and weighed dry) and,preferably between about 30 to 50 percent of the weight of the toweling.In particular, if the weight amount of solution employed is greater than50% of the weight of the toweling to be treated, strength loss will betoo great. Likewise, if the weight amount of the solution employed isless than about 10% of the weight of the toweling to be treated, thenthe cellulase will not impart the desired softening.

After application of the aqueous cellulase solution, the toweling isgenerally maintained under conditions sufficient to impart permanentsoftening to the toweling. Preferably, this includes maintaining thetoweling at an elevated temperature, i.e., about 20° C. to about 65° C.and preferably about 35° C. to about 60° C., for a period of time fromabout 1 to about 16 hours.

In another preferred embodiment, the toweling is maintained in anenvironment which does not permit substantial dehydration thereto. Underthese conditions, permanent softening is imparted to the toweling.

Without being limited to any theory, it is believed that the applicationof the aqueous cellulase solution to the surface(s) of cotton towelingexposes the cellulose in the fiber loops of the toweling to cellulasewhile minimizing exposure of the interior fibers, i.e., the base fabric,to cellulase. In this regard, FIG. 1A illustrates a plan view of acotton toweling, 1, and FIG. 1B illustrates an enlarged cross-sectionalview of cotton toweling, 1, taken along lines, 2—2. In FIG. 1B, fiberloops, 3, are found on the surface of toweling, 1, whereas, theremainder of the fiber is in the interior of toweling, 1. Since thefiber loops, 3, are generally on the surface of toweling, 1, applyingthe aqueous cellulase solution to the surface of the cotton toweling, 1,exposes these fiber loops to cellulase without exposing the interiorfibers to cellulase.

Again, without being limited to any theory, it is further believed thatthe action of the cellulase on the fiber loops results in some breakdownof the crystalline portion of cellulose in these loops which breakdownreduces the stiffness of the loop. Reduction in the stiffness of theloop results in permanent softening to the toweling which is achievedwithout the need to treat all of the cotton fibers in the toweling.

After maintaining the cotton toweling under conditions sufficient toimpart permanent softening to the toweling, the toweling is then treatedin a manner to remove and/or inactivate the cellulase enzyme. One methodof removing the enzyme is to thoroughly rinse the toweling with acellulase free aqueous solution. In such an embodiment, the toweling isthen dried at elevated temperatures (e.g., at a temperature of at leastabout 75° C.) to inactivate any enzyme remaining after rinsing.Alternatively, the treated toweling can be first after-treated toinactivate the cellulase enzyme by heating to sufficiently hightemperatures for a sufficiently long period of time to inactivate theenzyme (e.g., at a temperature of at least about 75° C. for a period ofat least 10 minutes). In this embodiment, the toweling is then usuallythoroughly rinsed and dried.

The methods of this invention are suitable for either a batch process ora continuous process. For example, in production, a preferredapplication of aqueous cellulase solution onto the surface(s) of cottontoweling can be carried out in a continuous manner and the treatedtoweling can be moved into a J-Box where the toweling will be maintainedunder conditions sufficient to impart permanent softening, e.g., 1-3hours at about 50° to about 60° C. The toweling can then be passedthrough a continuous rope washer containing a dilute cellulase solution(i.e., about 0.1 grams/liter to about 0.25 grams/liter at from about 50°C. to about 60° C.) and then thoroughly rinsed and dried. When a ropewasher is employed, it preferably contains a minimum of 4 bowls, andmore preferably 7 bowls to ensure complete enzymatic action on thecellulose which provides softening to the base fabric withoutunsatisfactory strength loss.

Alternatively, in a preferred batch process, after application of theaqueous cellulase solution to the surface(s) of cotton toweling, thetoweling can be rolled up, covered with plastic, and maintained underconditions sufficient to impart permanent softening, i.e., about 30° toabout 60° C. for about 1 to 8 hours. Afterwards, the toweling can thenbe passed through a continuous rope washer containing a dilute cellulasesolution (i.e., about 0.05 grams/liter to about 0.5 grams/liter at fromabout 50° C. to about 60° C.) and then thoroughly rinsed with acellulase free aqueous solution and then dried.

The use of a dilute cellulase solution in the continuous rope washerprovides for removal of loose fibers. However, the conditions are suchthat there is a minimal effect on additional strength loss in thetoweling.

FIG. 2 illustrates one means of continuously and simultaneously applyingan aqueous cellulase solution onto both surfaces of cotton toweling. InFIG. 2, apparatus, 4, comprises a cotton toweling, 5, which is stored atroller, 6, prior to application of the aqueous cellulase solution. Thedirection of that part of the toweling departing roller, 6, is changedby guide member, 7, so that the toweling is moving in a verticaldirection. While moving in a vertical direction, a requisite amount ofthe aqueous cellulase solution is applied onto the surfaces of toweling,5, via sprays, 8, which are generated from feedlines, 9. Feedlines, 9,are connected to a tank (not shown) containing a reservoir of theaqueous cellulase solution. If necessary, additional sprays, 6, can begenerated so as to cover more surface area or to provide a substantiallyuniform application of cellulase solution over the surfaces of thecotton toweling, 5. In general, application of the cellulase solutiononto the cotton toweling, 5, is considered substantially uniform if thevariation in application rate is no more than about ±2%.

After application of the aqueous cellulase solution, the direction oftoweling, 5, is changed by guide member, 10. Toweling, 5, can then bemoved to another roller (not shown) for batch treatment of the towelingunder conditions sufficient to impart permanent softening; or toweling,5, can be moved to a J-box for continuous treatment of toweling, 5,under conditions sufficient to impart permanent softening. In eithercase, after the toweling has completed treatment, it is generally sized(cut) into dimensions suitable for use as consumer goods.

The following examples are offered to illustrate the present inventionand should not be construed in any way as limiting its scope.

In these examples, the following abbreviations have the followingmeanings:

° C. = degree Centigrade ° F. = degree Fahrenheit g = gram l = liter lbs= pounds oz. = ounces

EXAMPLES Comparative Example A

Cotton toweling (made from 100% cotton terry cloth) was treated withcellulase in a prior art batch method to impart permanent softening.Specifically, samples of the same toweling were washed in differentaqueous cellulase solutions obtained by adding either about 0.4 g/l orabout 0.8 g/l of cellulase protein (from Primafast™ 100 cellulase,derived from Trichoderma reesei and which is available from Gresco Mfg.Co., Thomasville, N.C., 27360) to water. The aqueous solution wasbuffered at pH 4.5 to 5.0 by the addition of 3.6 g/l of acetic acid(56%) and 1.9 g/l of caustic (50%). The toweling was washed for 45minutes at 57° C. (135° F.), rinsed, and then dried.

Toweling treated with cellulase possessed improved softening; however,its physical properties were adversely affected as shown in Table Ibelow:

TABLE I TOWEL 0.8 g/l 0.4 g/l Standard Cellulase Cellulase Total Weight(oz) 16.22 11.92 11.22 Tensile Strength (lbs) Warp Direction 75 41 43Filling Direction 78 35 38 Absorbency*: 242 68 180 *Absorbency ismeasured in arbitrary units and higher absorbency values reflect moreabsorbent toweling

The above data demonstrates that prior art methods for treating cottontoweling result in substantial reductions in weight, tensile strength(in both the warp and filling direction) and in absorbency.

Example 1

Cotton toweling (made from 100% cotton terry cloth) was treated withcellulase in the manner of this invention to impart permanent softening.Specifically, the toweling was sprayed on both sides (25% wet add-on toeach side) with the following cellulase formulation:

0.4 g/l Cellulase Protein (from Primafast™100 Cellulase)

1.9 g/l Caustic, 50%

3.6 g/l Acetic Acid, 56%

0.5 g/l Nonionic Surfactant (wetting agent)

After spraying, the toweling was rolled up and secured in plastic toprevent moisture evaporation. The toweling was then batched for 2 hoursat 135° F. (56° C.); then removed and held in the washing machinecontaining 90 liters of the cellulase solution described above with theexception that the cellulose enzyme concentration was 0.2 g/l. Thetoweling was then washed at 135° F. (56° C.) for 30 minutes, rinsed andtumbled dried.

The so treated toweling possessed permanent softening and had thefollowing physical properties:

TOWEL Standard Example 1 Total Weight (oz) 16.22 13.54 Tensile Strength(lbs) Warp Direction 75 60 Fill Direction 78 62 Absorbency*: 150 235minimum *Absorbency is measured in arbitrary units and higher absorbencyvalues reflect more absorbent toweling

Example 2

An aqueous cellulase solution is applied to a cotton-containing towel(100% cotton terry cloth) in the manner of Example 1 above. Afterbatching the towel in a J-box for 1-3 hours at 57° C., the towel ispassed through a continuous washing step employing a rope washer having7 bowls. The first six bowls can contain the following solution:

0.2-1 g/l Cellulase Protein (from Primafast™ 100)

3.6 g/l Acetic acid, 56%

1.9 g/l Sodium Hydroxide, 50%

0.25-1.0 g/l Surfactant (optional)

Each of the first six bowls generally contains the same solution whereasthe 7th bowl can be used to deactivate the cellulase by utilizing anaqueous solution maintained at a temperature of 180-200° F. (82° to 93°C.). The cellulase can also be inactivated if the treated goods godirectly into a dryer after the continuous washing range. The time oftreatment in the continuous range should be 20-60 minutes. The speed ofthe fabric through the range will be controlled by the treatment minutesrequired to achieve the desired softness.

Similarly, by following the procedures set forth in Examples 1 and 2above, other cellulases, including cellulase derived from microorganismsother than Trichoderma reesei, could be employed merely by substitutingfor Primafast™100 cellulase. Other suitable cellulases which arecommercially available and which could be employed herein includeCELLUCAST, RAPIDASE, and the like. Likewise, the application of theaqueous cellulase solution to the surfaces of the cotton toweling can beachieved by any other art recognized methods including painting thesolution onto the surface(s) of the toweling and the like.

What is claimed is:
 1. A permanently soft cotton toweling manufacturedby treatment with cellulase prepared by the method comprising: (a)applying onto the surfaces of said toweling prior to application of afinish to said toweling an aqueous cellulase solution containing atleast about 0.2 grams per liter cellulase wherein the weight amount ofsaid aqueous cellulase solution applied onto the surface(s) of saidtoweling is between about 10 to 50 percent of the weight of saidtoweling and further wherein said aqueous cellulase solution is free ofsurfactant; (b) incubating the toweling at a temperature of from about20° to about 65° C. for a period of from about 1 to about 16 hours toimpart softening and/or inactivate the cellulase enzyme; (c) treatingthe cotton toweling in a manner to remove and/or inactivate thecellulase enzyme; wherein said cotton toweling after treatment whencompared to standard cotton toweling is characterized by retaining atleast: 83.47% of the total weight, 80% of the tensile strength in thewarp direction, and 79.48% of the tensile strength in the filldirection.
 2. The permanently soft cotton toweling according to claim 1,wherein the application of said aqueous cellulase solution to saidtoweling is by spraying and further wherein after incubation step (b)and prior to treating step (c) the cotton toweling is washed in acontinuous washer containing a dilute aqueous cellulase solution whichin the case where the toweling is produced from a continuous processcontains from about 0.1 to 0.25 grams of cellulase per liter of solutionand in the case where the toweling is produced from a batch processcontains from about 0.05 to 0.5 grams of cellulase per liter of solutionwherein the washing is conducted under conditions to remove loose fibersfrom the cotton toweling.
 3. The permanently soft cotton towelingaccording to claim 2 wherein the spraying of the aqueous cellulasesolution is over both surfaces of the toweling.
 4. The permanently softcotton toweling according to claim 3 wherein both surfaces of saidtoweling are sprayed simultaneously.
 5. The permanently soft cottontoweling according to claim 1 wherein said cellulase enzyme is removedby washing the toweling with a cellulase free aqueous solution.
 6. Thepermanently soft cotton toweling according to claim 5 wherein afterremoval of said enzyme, the toweling is dried at a temperaturesufficiently high to both dry the toweling and to inactivate anyremaining cellulase enzyme.
 7. The permanently soft cotton towelingaccording to claim 1 wherein said cellulase enzyme is inactivated byheating the toweling at a temperature and time sufficient to inactivatesaid enzyme.
 8. The permanently soft cotton toweling according to claim7 wherein said cellulase enzyme is inactivated by heating the cellulasecontaining cotton toweling to a temperature of at least 75° C. for atleast 10 minutes.
 9. The permanently soft cotton toweling according toclaim 7 wherein after inactivation of said enzyme, the toweling iswashed with a cellulase free aqueous solution and then dried.
 10. Thepermanently soft cotton toweling according to claim 1 wherein saidaqueous cellulase solution additionally contains a compatible buffer ata concentration of at least 0.005 N.
 11. The permanently soft cottontoweling according to claim 1 wherein said cellulase enzyme is derivedfrom a fungal microorganism.
 12. The permanently soft cotton towelingaccording to claim 11 wherein said fungal microorganism is selected fromthe group consisting of Trichoderma reesei, Trichoderma koningii,Pencillum sp., and Humicola isolens.
 13. The permanently soft cottontoweling according to claim 1 wherein said aqueous cellulase solutioncontains from about 0.2 to about 1 gram per liter of cellulase.
 14. Thepermanently soft cotton toweling according to claim 13 wherein saidaqueous cellulase solution contains about 0.4 grams per liter ofcellulase.